Effect of Eu2+ and Tb(2+)doping on structural, photoluminescence, thermodynamic and thermoelectric properties of celestine (SrSO4) phosphors

In this study, the density functional theory (DFT) based WIEN2K simulation code is used to calculate the ground state properties of [SrSO4]:Eu2+ and [SrSO4]:Tb2+ compounds with the help of FP-LAPW method. To determine the elec-trical and optical characteristics of Sr1-xAxSO4 (A = Eu2+, Tb2+), the Generalized gradient approximation with the addition of the Hubbard parameter (GGA + U) was utilized. The obtained band structure results of Sr1-xEuxSO4 com-pound show semiconducting nature (which is in the spin up (up arrow) state is 1.4eV while in the spin down (down arrow) state is 3.45eV), while the Sr1-xTbxSO4 compound depicts full-metallic nature through both spin states due to the crossing mechanisms of the conduction band minimum across the Fermi energy level. According to a theoretical assessment of optical prop-erties, the compounds under investigation are promising possibilities for active optical devices working in the Ultra violet region. We have demonstrated in this work the variation of temperature (0-500 K) and pressure (0-10 GPa) on seven key thermodynamic parameters by Using quasi harmonic Debye model. The thermoelectric properties have been calculated in the temperature interval 500 K <= T <= 800 K by using the Boltzmann simulation code. The finding shows that Sr1-xEuxSO4 and Sr1-xTbxSO4 compounds are promising for future advanced optical and thermoelectric devices.